Cytotoxic activity of chimeric proteins composed of acidic fibroblast growth factor and Pseudomonas exotoxin on a variety of cell types.

Chimeric proteins composed of acidic fibroblast growth factor (acidic FGF) and several forms of Pseudomonas exotoxin (PE) that cannot bind to the PE receptor have been produced in Escherichia coli by expressing chimeric genes in which DNA encoding acidic FGF is fused to various mutant forms of PE. These acidic FGF-PE fusion proteins were found to be cytotoxic to a variety of tumor cell lines including hepatocellular (PLC/PRF/5 and HEPG2), prostatic (LNCaP), colon (HT29), and breast (MCF-7) carcinomas at concentrations of 1-70 ng/ml. The cytotoxic effects of acidic FGF-PE were FGF-receptor specific as demonstrated by competition with excess acidic FGF and by showing that acidic FGF-PE bound to the FGF receptor with the same affinity as acidic FGF. Furthermore, the cell-killing activity of acidic FGF-PE was toxin-mediated, as an acidic FGF-PE mutant, which does not possess ADP-ribosylation activity, failed to kill cells. These findings demonstrate that acidic FGF-PE is a potent cytotoxic molecule that can be targeted to FGF receptor-bearing cells. Because acidic FGF is a potent angiogenic molecule, cytotoxic acidic FGF-PE chimeras may have utility as anti-angiogenic agents. These molecules could be helpful in determining the functional role of FGF receptors in cellular processes.